This invention relates to certain azlactone (oxazolone) compounds. More particularly, it relates to certain 2-alkenylphenyl-5-oxazolones useful in the production of homopolymers and copolymers having pendant functional groups obtained by ring-opening addition to azlactone (oxazolone) groups.
Monomeric and polymeric azlactones (also known as oxazolones) are well known and have been described in numerous patent and other publications. The functionality of their pendant azlactone groups, particularly the reaction of such groups with nucleophilic materials, and without production of by-product materials, has also been reported. For example, polymerizable azlactones, and their use in the production of homopolymers and copolymers having versatility in the production of useful polymeric products, have been described in U.S. Pat. No. 3,488,327 (issued Jan. 6, 1970 to F. Kollinsky et al.); in U.S. Pat. No. 3,583,950 (issued Jun. 8, 1971 to F. Kollinsky et al.); in U.S. Pat. No. 4,304,705 (issued Dec. 8, 1981 to S. M. Heilmmann et al.); in U.S. Pat. No. 4,737,560 (issued Apr. 12, 1988 to S. M. Heilmann et al.); by Iwakura, et al., in Journal of Polymer Science, Vol. 6, pp. 2681-2684 (1968); by L. D. Taylor, et al., in Makromol. Chem., Rapid Commun. 3, 779-782 (1982); and by J. K. Rassmussen, et al., in Encycl. Polm. Sci. Eng., Second Edition, H. F. Mark, N. Bikales, C. G. Overberger and G. Menges, Editors, Wiley, New York, N.Y., Vol. 11, pp. 558-571 (1988).
Among azlactone compounds which have been the focus of considerable attention, by reason of their potential value in the production of highly versatile functional polymers, is the monomer, 2-vinyl-4,4-dimethyl-5-oxazolone, prepared and reported by K. Hubner et al., in Angew. Makromol. Chem. 11, 109 (1970). Reported advantages of this monomer include ease of preparation, stability and reactivity of the anhydride group thereof by addition, with no by-product formation. L. D. Taylor, et al., Makromol. Chem. Rapid Commun. 3, 779-782 (1982). Azlactone polymers in the form of homopolymers are, in general, insoluble in water and only poorly wetted by water. The homopolymer of 2-vinyl-4,4-dimethyl-5-oxazolone (VDMO) is, for example, soluble in organic solvents such as chloroform, dichloromethane, dimethylformamide or tetrahydrofuran, and, if kept very dry, in ethyl acetate, benzene or acetone--as reported by L. D. Taylor, et al., in Makromol. Chem. Rapid Commun. 3, 779-792 (1982). The homopolymer is insoluble in water and poor wettable.
In the production of useful polymeric products from derivatizable azlactone monomers, it will oftentimes be preferred to first form an azlactone polymer having certain predetermined physical and solubility characteristics, in contemplation of the intended use for the derivatized and functional polymeric product, and to then react the azlactone groups of the resulting azlactone polymer with the derivatizing and functionally useful compound. Particularly where the derivatized polymer is to be used in an aqueous medium, the desired properties of the derivatizable azlactone polymer may be the result of copolymerization of a polymerizable monomeric azlactone with another ethylenically unsaturated polymerizable monomer. In general, production of useful derivatizable polymers, and particularly copolymers, will depend upon the polymerizability, i.e., the polymerization reactivity, of the azlactone monomer. For example, an intended production of an azlactone copolymer from an azlactone monomer and another copolymerizable monomer may lead only to an azlactone homopolymer or to the production of a copolymer containing repeating units in proportions substantially different from the proportions of monomers used in the polymerization. Moreover, copolymerizable monomers having desired hydrophilicity will oftentimes contain nucleophilic moieties, such as hydroxyl or amino groups, which may interfere with desired copolymerization by undesired ring-opening reaction with pendant azlactone groups.
If desired, a polymerizable azlactone monomer can be reacted with a functionally useful derivatizing agent prior to production of a homopolymer or copolymer. It will be appreciated that the polymerizability of the derivatized monomer will be influenced by the nature of the moiety introduced into the monomer by such derivatization. The carbon-carbon double bond of the azlactone monomer may also be the site of a competing and undesired reaction during derivatization of the monomer. While the anhydride group of the azlactone heterocycle shows good ring-opening reactivity without by-product formation, it has been reported that certain sulfur compounds and bulky secondary amines react with alkenyl azlactones at the carbon-carbon double bond (by a 1,4- or Michael-addition reaction), and under certain conditions, at the most polarized electrophilic center, i.e., at the carbonyl group (J. K. Rasmussen, et a;., Advances in Polymer Synthesis, B. M. Culbertson and J. E. McGrath, Editors, Plenum Publishing Corp., New York, 1985, p. 230).
It will be appreciated that an alkenyl azlactone monomer which exhibits good polymerization activity, such that homopolymers and copolymers can be readily produced therefrom, and which has the ring-opening reactivity of pendant azlactone groups in monomeric or polymeric form, will be advantageous. A polymerizable alkenyl azlactone which can be derivatized for use in the production of useful polymers, with little or no attending involvement of the alkenyl group in an undesired Michael addition reaction, will be of particular advantage in the production of functional polymeric derivatives.